Programmable Read-Only Memory. Read-only memory which can be programmed by the user using a special hardware programmer.

The closeness of agreement among measurements of the same value of the same quantity where the individual measurements are made under different defined conditions, i.e. by different methods or with different measuring instruments.

A class of rain gauge in which the level of the collected rain water is measured by the position of a float resting on the surface of the water.

Particle on which the freezing of water occurs.

A unit of distance equal to 5280 feet. It is sometimes referred to as a land mile.

Anemometer whicb measures wind speed by measuring the degree of cooling of a metal wire heated by an electric current. A type of cooling power anemometer.

The time required for an instrument to registe 63.2% of a step change in the variable being measured.

Any horizontal wind velocity tangent to the contour line of a constant pressure surface (or to the isobar of a geopotential surface) at the point in question.

The amount of sky covered or concealed by clouds or obscuring phenomena. It is reported in tenths, so that 0.0 indicates a clear sky and 1.0 (or 10/10) indicates a completely covered sky. The following classifications are used in aviation weather observat ...

The quantity to be measured (or modulated, or detected, or operated upon) which is received by an instrument. Thus, for a thermometer. temperature is the input quantity.

The record or trace made by a microbarograph.

An instrument for measuring the relative speed of a fluid. It consists of a concentric pipe arrangement in which the inner pipe is open at one end and the outer pipe is perforated and closed at both ends. Each pipe is connected to a manometer. The unit is ...

Very small precipitation drops (diameters less than 0.5 mm) that appear to float with air currents while falling in an irregular path. Unlike fog droplets, drizzle falls to the ground.

variable audio-modulated radiosonde developed at the Bureau of Standards and used by the United States weather services.

Abbreviation for radio frequency.

Of or pertaining to rain.

A seasonal wind of persistent direction, characterized by a pronounced change in direction between seasons.

The time required for an instrument to register a designated percentage (frequently 90%) of a step change in the variable being measured.

The atmospheric pressure computed using station elevation as the reference datum level. Station pressure is usually the base value from which sea level pressure and altimeter setting are determined.

A mercury barometer of the fixed cistern type in which a moveable scale terminating in an ivory point is used to compensate for the variations in the height of the mercury in the cistern